Identification of a gene overexpressed in aphids reared under short photoperiod

Most aphids develop a cyclic parthenogenesis life-cycle. After several generations of viviparously produced parthenogenetic females, follows a single annual generation of sexual individuals, usually in autumn, that mate and lay the sexual eggs. Shortening of photoperiod at the end of the summer (together with temperature) is a key factor inducing the sexual response. Currently no genes involved in the cascade of events that lead to the appearance of sexual forms have been reported. After a Differential Display RT-PCR survey performed on Acyrthosiphon pisum aphids, we identified a gene that is overexpressed in aphids reared under short photoperiod conditions that induce sexuality in this species. This cDNA (called ApSDI-1) shows similarities with a protein involved in amino acid transport in GABAergic neurons. Since several studies implicate GABAergic transmission in the generation and modulation of circadian rhythmicity, we propose that ApSDI-1 could be involved in the transduction of the photoperiodic message and therefore be a candidate to participate at some point in processes that trigger the sexual response in aphids. This is the first gene identified in aphids whose expression is governed by the photoperiod. (C) 2003 Elsevier Science Ltd. All rights reserved.